This application claims the benefit of Japanese Patent Application No. 2001-253771, filed Aug. 24, 2001 entitled xe2x80x9cFAN FILTER UNIT CONTROL SYSTEM AND CLEAN ROOM PROVIDED WITH SAME.xe2x80x9d
The present invention relates to a clean room, in which electronic devices such as semiconductor devices and liquid crystals are manufactured, and more particularly to a fan filter unit control system for controlling the operation of fan filter units (referred below to as xe2x80x9cFFUsxe2x80x9d) provided in a ceiling of the clean room and a clean room equipped with the same.
In general, cleanliness of a clean room is classified into class 1, class 10, class 100 or class 1,000 in accordance with manufacturing processes in the clean room. Such cleanliness is classified in accordance with the number of times of circulation of air flow that varies depending upon a wind velocity, at which the air flow is blown from the FFUs, and the filter grade of HEPA filters, ULPA filters and so on. In recent years, PTFE filters free of generation of boron gases and low-boron filters involving reduction in an amount of boron generated from glass fiber filters are used properly every manufacturing process.
In order to obtain a high level of cleanliness of around class 1 or class 10 in a clean room, not only the number of times of circulation of air flow in the clean room but also directions of air flow in the clean room constitute important factors.
A conventional FFU 1, as shown in FIG. 16, uses a motor 4 to rotate a fan 3 to draw an air through an inlet port 7, and a filter 2 below the FFU 1 filters the air to blow out a clean air 9. Cleanliness in a clean room is maintained by adjusting the velocity and direction of the clean air 9 blown.
As disclosed in JP-A-11-218353 (prior art 1), as a means for adjusting the wind velocity into the clean room from FFUs, pressure difference sensors are provided upstream and downstream of filters of the FFUs to detect static pressures of the filters 2 and calculate the blowing wind velocities of the FFUs from static pressure-air volume characteristic of the filters, thus controlling the wind velocities with the use of a motor revolution speed control means.
Further, JP-A-9-96431 (prior art 2) describes a control method, in which air volume adjusting plates are provided on a floor in a clean room to prevent turbulence in a down-flow in the clean room, and an air volume passing through vents in the floor is measured to provide control so as to ensure a constant air volume.
With the prior art 1 described above, the pressure difference sensors provided in the respective FFUs are used in adjusting the wind velocity of an air blown therefrom, but no account is taken of controlling directions of air flows in the clean room based on information of positions of the FFUs provided in the ceiling of the clean room and pressure in a ceiling chamber.
Also, with the prior art 2, it is described that air volumes of air flows through the vents in the floor of the clean room are measured so as to make air volumes constant on the floor, but no account is taken of controlling an air volume of air flow in the clean room by measuring the wind velocity in the clean room.
As described above, none of the prior arts is insufficient to improve cleanliness in the clean room.
An object of the present invention is to provide an FFU control system capable of controlling directions and air volumes of air flows blown from FFUs provided in a ceiling portion of a clean room in order to improve cleanliness in the clean room.
Another object of the present invention is to provide a clean room provided with a control system that makes pressure in a ceiling chamber uniform and facilitates the revolution speed control on the FFUs in order to improve the wind velocity distribution in the clean room.
Still another object of the present invention is to provide a clean room provided with a damper adjusting mechanism provided under a grating floor in the clean room in order to control the direction of air flow in the clean room.
To achieve the above objects, the invention provides a fan filter unit control system comprising fan filter units provided in a ceiling of a clean room; and a control device for controlling the fan filter units; and wherein revolution speeds of fan motors for the fan filter units are controlled in accordance with information about positions of the fan filter units and information about pressures detected by differential pressure gauges provided in a ceiling chamber of the clean room.
Also, the fan filter unit control system is constructed such that air volumes calculated after revolution speeds of the fan motors have been controlled are displayed on a control screen.
Also, a clean room comprises the fan filter unit control system and fans provided in a ceiling thereof, and is constructed such that the fans in the ceiling of the clean room are controlled by information from differential pressure gauges provided in a ceiling chamber.
Also, a clean room comprises fan filter units provided in a ceiling of the clean room, a control device for controlling the fan filter units, wind velocity gauges provided in the clean room, and fans provided under a floor of the clean room, and is constructed such that revolutions of the underfloor fans are controlled in accordance with information from the wind velocity gauges.
Also, a clean room comprises fan filter units provided in a ceiling of the clean room, a control device for controlling the fan filter units, wind velocity gauges provided in the clean room, and dampers provided under a floor of the clean room, and is constructed such that the opening ratios of the underfloor dampers are controlled in accordance with information from the wind velocity gauges.
Also, a clean room comprises fan filter units provided in a ceiling of the clean room, a control device for controlling the fan filter units, wind velocity gauges provided in the clean room, and a grating floor of the clean room and adjustable in opening ratio, and is constructed such that the opening ratio of the grating floor is controlled in accordance with information from the wind velocity gauges.
Also, a clean room comprises fan filter units provided in a ceiling of the clean room, a control device for controlling the fan filter units, and differential pressure gauges provided in the fan filter units, and is constructed such that the service lives of the fan filter units are calculated based on information from the differential pressure gauge provided in the fan filter unit and are displayed on a screen.